More contrast between button states

```
When touching a button, the visual difference between the button-up and
button-down states is very minimal. My coworker said that it was particularly
hard to see and didn't know that I had touched something when I demoed it to
her.

In the Toolbook demo, the buttons undergo a much more drastic color change
(almost a reverse) in the button-down state. Blue-when-up buttons turn yellow
when down. The font changes from white to black as well. This exact color
scheme does not have to be followed, but the buttons should look obviously
different when somebody is touching one.

```

Original issue reported on code.google.com by `jbjor...@gmail.com` on 20 Aug 2013 at 4:57